1. Field of the Invention
The present invention relates to a conveyance apparatus which conveys a sheet using, for example, two conveyance units equipped with encoders, a control method therefor, and a printing apparatus.
2. Description of the Related Art
For example, an inkjet printing apparatus comprises an LF roller and discharge roller as a mechanism for conveying a sheet. When conveying a sheet, the inkjet printing apparatus uses the LF roller as a main conveyance unit, and the discharge roller as an auxiliary unit.
In the positional relationship between these two rollers, an area where the printhead scans is defined as that between the LF roller arranged on the upstream side and the discharge roller arranged on the downstream side. Hence, the print area is an area corresponding to a printhead scan area defined when the LF roller and discharge roller hold print paper.
The print area is also an area corresponding to a printhead scan area defined when only the discharge roller conveys print paper. That is, the inkjet printing apparatus prints even in an area at the trailing end of print paper.
When printing in the trailing end area, the number of nozzles for use in the printhead is decreased to reduce the amount of conveyance by one conveyance operation in order to compensate for a drop in conveyance precision (Japanese Patent Laid-open No. 2004-230817).
However, this arrangement decreases the amount of conveyance by one conveyance operation. This increases the number of printhead scan operations and the number of conveyance operations, and lowers the throughput.
As another method, not only the LF roller but also the discharge roller comprise encoders to control conveyance. However, neither a concrete control method nor an arrangement when controlling conveyance using two encoders has been established.